The present invention relates to the transmission of data and, in particular, to data sets.
Workers in the data transmission art, particularly in the area of voiceband data transmission, have suggested various data set, or modem, designs which, in some way, operate under programmed processor, e.g., microprocessor, control. One advantage of such processor-based data sets is that the data set design can be updated relatively inexpensively via program modification both during development of the design and after full-scale manufacturing has begun. Another advantage is that the data set can, with relative ease, be designed to operate with, for example, a number of signaling rates and modulation formats. Moreover, incorporating a programmed processor into the design makes it economically feasible to provide the data set with sophisticated features, particularly in the area of data set and network diagnostics.
The present invention is useful principally in processor-based data sets of a type in which the real-time processing of user-provided data and/or received data signals is performed by special-purpose signal processing circuitry. The signal processing circuitry, more particularly, is capable of operating, for example, in accordance with various operating parameter values, such as carrier frequency and bit rate. It is also capable of operating in accordance with various signal processing formats, such as scrambler/descrambler and differential encoding/decoding algorithms and modulation formats. The data set further includes a controller at the heart of which is a programmed processor. The data set controller writes information signals into various registers (signal holding circuits) within the signal processing circuitry via a primary data bus, those information signals specifying the particular operating parameters and signal processing formats which are to be used at any given time by the signal processing circuitry. The data set controller is also capable of reading information from various registers to, for example, monitor the operation of the signal processing circuitry.
The capability of the signal processing circuitry to operate at different times in accordance with various operating parameter values and signal processing formats is advantageous in that it allows the same signal processing circuitry and overall data set architecture to be used in a family of data sets, i.e., data sets which operate at various speeds and in accordance with various Bell System, CCITT, or other formats. This capability may also be used to advantage to, for example, effect the changes in data set operation attendant to transitions between start-ups, normal data transmission and recovery, and turn-offs.